1. Field of the Invention
The present invention relates to an exchange for executing connections among a plurality of terminals via a plurality of communication channels.
2. Description of the Related Art
As one of functions carried out by an exchange, there has been available a camp-on function. According to the camp-on function, when a certain terminal (calling terminal) makes a call to another terminal (called terminal) while the called terminal is used or busy, the calling terminal reserves at an exchange a connection, i.e. a camp-on, between itself and the called terminal and, when the called terminal becomes idle, the exchange calls up the called terminal and then the calling terminal so as to execute the reserved connection, i.e. the reserved camp-on. In general, each terminal is allocated one communication channel independently. Thus, when a certain terminal is used, it means that a channel for that terminal is also used. Under these circumstances, the conventional exchange only monitors whether each terminal is used or not, for carrying out the reserved camp-on.
Recently, however, one channel is shared by a plurality of terminals for efficient utilization of the channel, or one terminal uses two or more channels for the speed-up of communication. Therefore, it may take place that although a camp-on-reserved calling or called terminal is idle, a corresponding channel is used by another terminal, or that although a channel is idle, a corresponding camp-on-reserved calling or called terminal is busy.
As described above, since the conventional exchange merely monitors whether each terminal is used or not, there has been a problem that it is difficult to reliably execute the reserved camp-on.